Enhanced control systems including flexible shielding and support systems for electrosurgical applications

ABSTRACT

An active electrode probe for an enhanced control surgery system is disclosed. The probe has a flexible conductor for delivering electrosurgical energy during an electrosurgical procedure, and is adapted for connection to an electrosurgical generator. The probe also has a flexible electrical insulation substantially surrounding the conductor. The probe also has a flexible conductive shield substantially enclosing the electrical insulation, the flexible conductive shield electrically connected to a reference potential, whereby any current which flows in the flexible conductive shield from the conductor is conducted to the reference potential. The flexible conductive shield is formed from a conductive wire.

PRIORITY AND RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.13/788,714 filed on Mar. 7, 2013, which is a divisional application of,and claims the benefit of, U.S. application Ser. No. 12/543,344 filed onAug. 18, 2009, now U.S. Pat. No. 8,500,728, which claims the benefit ofProvisional U.S. Application No. 61/089,668 filed on Aug. 18, 2008, theentire disclosures of which are incorporated by reference for all properpurposes.

FIELD OF THE INVENTION

Aspects of the present invention relate to electrosurgical procedures,techniques, and devices that utilize enhanced control systems such asrobotics and other motion control apparatus. Aspect of the presentinvention also relate to electrosurgical systems with a monitored safetysystem capable of monitoring both the electrosurgical instruments andany neutral instruments or other conductive surfaces in the generalvicinity of the surgical site.

BACKGROUND

Enhanced control surgery (ECS) systems broadly refers to devices andsystems that consist of mechanical or electro-mechanical configurationsand that may provide one or more enhanced endo-mechanical features thatenable a surgeon with improved surgical end effector mobility. Examplesof such improvements include increased instrument flexibility, betterergonomic positioning, hand tremor reduction, translation of motionframes of reference, telesurgery, robotic surgery systems and the like.ECS systems typically include more elaborate instruments and supportstructures when compared to traditional laparoscopic surgery and mayalso include the use of novel body entry devices and different points ofentry compared to laparoscopic or other minimally invasive surgicaltechniques.

Electrosurgical systems have utilized Active Electrode Monitoring(“AEM”) for several years, such as AEM monitor systems manufactured byEncision, Inc. of Boulder, Colo. These systems are generally describedin U.S. Pat. No. 5,312,401 and related patents. Despite the successobtained, and increased patient safety realized, by the inventionsembodied in the '401 patent, as well as the electrosurgical tools thatembody those inventions, there remain certain problems and drawbackswhen applied to ECS systems.

These drawbacks include, among other things, 1) the need to provideinstrument shielding on structures that are not rigid shafts and thatinclude complex articulating geometries found in ECS systems and tools,and 2) the need to monitor one or more non-electrosurgical instruments.As used herein, the term “cold instrument” refers to a surgical tool ordevice that does not have or is not meant to have electrosurgical energyactively applied to it or its end effector. These cold instruments can,under certain conditions, conduct electrical energy that can becomeharmful to the patient and cause burns. The same harmful conditions thatcan provide electrical energy to the cold instruments can also effectfloating conductive surfaces that might also be in contact with thepatient or operating room staff, such as the operating table or themechanical support structure used to hold and control the ECS systems.

Current procedures used in minimally invasive electrosurgery utilizemultiple access ports for the various instruments. Though devices suchas the Encision AEM® monitoring system protect the active electrodeinstrument, the potential still exists that the surgeon mightinadvertently or purposefully touch another instrument such as a grasperor optical scope with the active and electrically charged instrument.This additional instrument then has the potential to transfer electricalenergy directly to the patient in an area that may not be visible to thesurgeon. In addition, new surgical techniques involving single portaccess surgery (SPA), robotic surgery, and natural orifice transluminalendoscopy (NOTES) position the instruments in even closer proximity toeach other and contain more non-referenced conductive surfaces that caninadvertently carry electrical energy. While SPA apparatus (instrumentsand cannulae) are generally not used for ECS systems as described above,they involve different points of entry compared to traditionallaparoscopic surgery. For instance, SPA surgery might be used forcosmetic reasons, reduced pain, and reduced chance for herniation.Because all instruments pass through a single incision (e.g. theumbilicus) they are very close together and increase the likelihood ofcross-coupling of energy compared to traditional laparoscopic surgery.This highlights the need for both active instrument protection and forcold instrument monitoring and protection.

Thus, there is a need for a better way to provide a monitoredelectrosurgical energy to the primary “hot” instrument while alsomonitoring for inadvertent stray electrosurgical energy in coldinstruments and other conductive surfaces. In addition, because of theadded degrees of freedom and the need to accommodate advanced monitoringtechniques in the more complex and larger scale instruments beingutilized in ECS surgical techniques, prior monitoring techniques used inrigid shaft embodiments are not adequate.

SUMMARY

In one example, an active electrode probe for an enhanced controlsurgery system is provided. The probe has a flexible conductor fordelivering electrosurgical energy during an electrosurgical procedure,and the conductor is adapted for connection to an electrosurgicalgenerator. The probe also has a flexible electrical insulationsubstantially surrounding the conductor. The probe also has a flexibleconductive shield substantially enclosing the electrical insulation. Theflexible conductive shield is electrically connected to a referencepotential, whereby any current which flows in the flexible conductiveshield from the conductor is conducted to the reference potential. Theflexible conductive shield is formed from a conductive wire.

In another example, an electrosurgical instrument is provided. Theinstrument has an instrument segment having a proximal end and a distalend, and an end effector articulably coupled to the distal end of theinstrument segment. The end effector has an active electrode and isconfigured to perform an electrosurgical procedure. The instrument alsohas a flexible shield configured to transmit normal current and faultcurrent to an active electrode monitoring system during theelectrosurgical procedure. The flexible shield surrounds at least aportion of the instrument segment and a portion of the end effector. Theflexible shield is shaped and positioned to maintain an adequatecreepage spacing between the flexible shield and the active electrode.

In another example, a shield for an electrosurgical instrument isprovided. The shield has a first layer having a flexible non-conductivematerial, a second layer disposed on the first layer and having aflexible conductive medium, and a third layer disposed on the secondlayer and having a flexible non-conductive material. The flexible shieldis configured to isolate an electrosurgical active conductor and towithstand a power having a voltage of up to 5 kilovolts or a faultcurrent of 2.0 Amperes or greater.

Other aspects will become apparent to one of skill in the art upon areview of the following drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a generalized diagram of an enhanced control surgical system;

FIG. 1B is a drawing of one embodiment of a control arm used in anenhanced control surgical system;

FIG. 1C is a detail of one embodiment of an articulated control armmember of an enhanced control surgical system;

FIGS. 1D and 1E are depictions of a single port access procedureutilizing three surgical tools;

FIGS. 2A-2C are the various frequency spectrums exhibited during anelectrosurgical procedure;

FIGS. 3A and 3B are diagrams that show the variations in impedance underconditions similar to those in FIGS. 2A-2C;

FIGS. 4A-4D show various embodiments of flexible circuits that may beutilized to construct the shield element in monitoring ECS systems;

FIG. 5A shows one embodiment of a device for sensing the voltage on thesurface of a cold surgical instrument;

FIG. 5B shows one embodiment of a multi-channel monitoring system;

FIG. 6 shows one aspect of a device constructed in accordance withaspects of the present invention;

FIGS. 7A and 7B shows another aspect of a device constructed inaccordance with aspects of the present invention;

FIG. 8 shows a view of a single point entry procedure in accordance withvarious aspects of the present invention;

FIG. 9 shows a view of a single point entry procedure in accordance withanother aspect of the present invention;

FIG. 10 shows a generalized ECS system setup that utilizes cold toolmonitoring in accordance with various aspects of the present invention;

FIG. 11 illustrates a side section view of a distal region of anexemplary surgical instrument;

FIG. 12 is a side section view of a shield which may be used in theinstrument illustrated in FIG. 11;

FIG. 13 is a cross-section view of an exemplary insulated wireimplemented in some examples;

FIG. 14 is side section view of another exemplary shield which may beused in the instrument illustrated in FIG. 11;

FIG. 15 is a perspective view of an exemplary shielded boot assembled onthe articulated control arm member illustrated in FIG. 1C; and

FIG. 16 is a perspective view of an exemplary shielded boot assembled oncontrol arm illustrated in FIG. 1B.

DETAILED DESCRIPTION

The term ECS refers to both Enhanced Control Surgery systems as a wholeas well as one or more of the components utilized in such procedures.These may include robotic arms and the individual components,controllers, and other complex mechanical devices used in the roboticsystems, as well as any specialty tools or structures used to performthe surgical procedure. While providing a heightened degree of controland accuracy, certain implementations of ECS may involve a field of viewthat is even more limited than in traditional laparoscopic surgery. Thisoccurs in part because the surgeon may not have the ability to pan acamera inside the patient and may not have direct vision at the portsites. In addition, due to the small size of individual components(including conductors) in ECS and other flexible systems, there is anincreased risk of electrical breakdown due to both mechanical andelectrical stress. Breakdown may be within the instrument or in theconductor system and may include conduction to shielding components orto the ECS support structure.

ECS tools and systems offer the ability to deliver various forms ofelectrical power depending on the type of surgery or procedure involved.Thus, there is a need for shielding and protective monitoring in bipolarmodes (both electrodes in instrument and both surgically active),sesquipolar modes (both electrodes in instrument but only one electrodesurgically active) as well as monopolar modes (one electrode ininstrument, the other as a remote return electrode) electrosurgicalsystems. In all electrosurgical modes the objective is to protect thepatient and users from the harmful effects of insulation failure,capacitive coupling and current inadvertently conducted through coldinstruments and support structures.

In ECS systems the potential for cross coupling between an activeinstrument and an adjacent cold instrument or other conductive objectmay need to be controlled differently than in open or laparoscopicsurgery. This is at least partially due to the fact that there may bemore conductive objects in closer proximity to each other combined withless opportunity for direct visualization. This is further problematicbecause an ECS tool may be activated either directly with controls nearthe patient, or remotely.

In ECS applications, surgery may also take place in an extremelyconfined space. This could be for example within an organ or thevascular system. In these situations an electrosurgical active electrodemay contact other instruments not intended to be electrified, or contactother conductive objects within the body. Under these conditions it isdesirable to limit energy delivery so that excessive heating to theconductive object or to body tissue does not occur. Under extremeconditions welding can occur between the electrode and the contactedobject and this is particularly important to avoid.

Typically when there is sparking between metallic objects, there is acharacteristic frequency spectrum of the conducted current that isdifferent from the spectrum of current delivered to tissue in normalelectro surgery. This spectral difference in active current of theelectrosurgical system can be sensed and used to determine the presenceof a fault condition.

FIG. 1A is high-level representation of a common embodiment of an ECSsystem 100. Major components of such a system include a supportstructure 102, actuation means 104, and one or more flexible orotherwise articulating elements or control arms 106 a, 106 b, and 106 c.As with traditional surgical techniques, a patient 108 is supported onan operating table 110 positioned next to and/or underneath the surgicalsystem 100. A control terminal 115, such as a computer or otherinterface, is available to interact with the ECS system 100 and isadapted to allow a user to control the one or more control arms 106a-106 c in order to perform the surgical procedure. The control terminal115 may be located adjacent to the ECS system 100 in the same operatingroom, may be in an adjacent (e.g., non-sterile) room, or may be at aremote site from the surgical procedure itself. Various computer screensand/or other monitoring devices may be located in and around the ECSsystem 100 in order to convey information to the operating room staff.

FIG. 1B is representative of one of the control arm elements 106 a fromFIG. 1A and more particularly shows one embodiment of the articulatingand movable nature of the control arm element 106 a. Control arm 106 aincludes a connector 120 or other interface that mounts to or engageswith the support structure 102. Control arm 106 a ultimately interfaceswith control terminal 115 where an operator or surgeon can control themovements of the control arm 106 a. An articulation mechanism 125connects to an elongated segment 130 and preferably provides threedegrees of movement to the segment 130. The length of segment 130 variesin different embodiments depending on the specific type of procedurebeing effected. Articulation mechanism 125 provides a bendable androtatable joint (also referred to as a wrist) for an operator tomaneuver in order to move the segment 130 into a desired position inthree dimensional space. A second articulation mechanism 140 connectsthe segment 130 with an end effector 135. In one embodiment, the endeffector is an active electrode for performing an electrosurgicalprocedure. In FIG. 1B, the end effector is shown as a grasper. Variousother end effectors may be utilized as well including both cold and hotinstrument configurations.

FIG. 1C shows one embodiment of a detailed articulation mechanism 125.FIG. 1C is one type of “wrist” mechanism as can be seen by the abilityof the joint to move in many degrees of freedom such as a human wristcan. Mechanism 125 includes interconnected sections 152, 153, 160, and162 that rotate, pivot and bend with respect to each other. Section 152is adapted to engage in one embodiment with an elongate member that inturn holds an end effector or other tool for performing a surgicalprocedure. Exemplary embodiments and further details of these types ofcomplex ECS devices can be found in U.S. Pat. No. 6,817,974, the detailsof which are incorporated herein by reference. The aspects disclosed inthe present application are meant to have applicability to these andrelated ECS control systems. Mechanism 125 further includes variouspassageways 154 and 158 that provide a path for one or more conductorsor other control wires to pass from one end of the mechanism to theother, while also being capable of following the curves and othermanipulations within the geometry of the mechanism 125. As shown in FIG.1C, various control wires or other conductors 150 are able to pass tothe distal end of the device that include an end effector.

As described in more detail below, an active electrode, as well as anyshielding structure associated with that electrode, that extends throughthe entire element 106 a (including mechanism 125 from FIG. 1C) needs tobe able to function properly while flexing, bending and/or twistingthrough the articulation mechanisms 125 and 140.

While particularly applicable to ECS procedures and the complex devicesdescribed above, the need to monitor the non-energized tools used in asurgical procedure also extends to single point access procedures. FIGS.1D and 1E show the general orientation of three tools used in a singlepoint entry procedure. An active electrosurgical (“hot”) tool 560, alaparoscopic camera 562, and a third instrument 564 are all shownaccessing a surgical site through a trocar cannula or other surgicaltool introducer device at common entry point 566. In this embodiment,camera 562 and instrument 564 are “cold” and are thus not intended tocarry electrical energy as the electrosurgical instrument 560 is meantto. The three surgical tools are meant to perform a surgical procedureat their distal ends 561, 563, and 565, and remain electrically isolatedfrom each other. However, in this situation, the proximity of the threetools results in an area 567 where capacitive coupling from theelectrosurgical instrument 560, a breakdown in the electrosurgicalinstrument's insulation, or inadvertent touching between theelectrosurgical instrument 560 and one of the other instruments, willcause energy to be inadvertently transferred to the cold instruments 562and 564 and eventually to the distal ends 563 and 565 of thoseinstruments to a point in the body tissue where an electrical dischargeis not desired. Among other things, monitoring and protection againstthese types of inadvertent burns is addressed by aspects of the presentinvention. Various new techniques can be used to detect these unsafeconditions.

Various Conventional electrosurgical applications (e.g. those involvinga single rigid shaft tool) create a load impedance within a certainrange. That load impedance range depends on the electrode size andtissue type, among other variables. If during an ECS procedure, anactive electrode contacts a separate instrument or another conductiveobject that is not meant to be electrically active, the load impedancevalue may fall below the otherwise normal range. Thus, sensing the loadimpedance and using its value in a calculation can aid in the detectionof a fault condition under these circumstances.

Also in conventional electrosurgical applications, the load impedancechanges in a known fashion, generally starting at a relatively low valueand progressing as the contacted tissue dries to a higher value. In anabnormal condition (e.g. where the active electrode contacts anotherconductive object), the pattern of impedance change may be downward withstabilization at a low value. One or more of this load impedance rate ofchange, the direction of change along the load impedance curve, and aspectral determination may then be used to detect any abnormal contactconditions. When such conditions are detected, a monitoring device isprogrammed to respond by reducing or ceasing the application of power tothe active electrode.

FIGS. 2A, 2B and 2C show various frequency spectrums under the differentconditions described above and how contact with a normally non-energizedinstrument can result in the production of abnormal energy that needs tobe avoided. For example, FIG. 2A shows a normal voltage waveform 200under driving conditions, FIG. 2B shows the waveform 210 when the activeelectrode is in contact with tissue during a surgical procedure, andFIG. 2C shows the waveform 220 when the active electrode unintentionallycomes into contact with a metallic or otherwise conductive object. Theshaded area 225 in FIG. 2C represents the abnormal and unintended energythat ends up being delivered to the patient tissue under this condition.It is the abnormal condition represented by area 225 that needs to bemonitored and/or prevented.

Turning to FIGS. 3A and 3B, these diagrams show the variations inimpedance under conditions similar to those in FIGS. 2A-2C. FIG. 3Ashows the expected variation of impedance under normal (300) andabnormal (305) conditions. The illustrated case shows the abnormalconditions placing the measured Z value below the normal range R. Thisexample is indicative of a fault condition that would trigger themonitoring system to alter or cease power delivery to the activeelectrode.

FIG. 3B shows the expected variations in the time durations of impedancein the normal and abnormal conditions of FIG. 3A. Here, the abnormalcondition 305 generates a negative spike which exceeds the expectedrange for normal conditions (the dashed “threshold” line 310) and isalso indicative of a fault condition that would trigger the monitoringsystem to alter the user or cease power delivery to the activeelectrode.

Various embodiments are contemplated for sensing the presence of thisabnormal energy. For example, an adaptive filter might be utilized thatis sensitive to the driving waveform, and can be used to detect smalldifferences in spectral energy. Either of the above evaluations can beused to determine the presence of a fault condition or they may be usedin combination to determine a fault condition.

With the popularity of ECS systems providing additional degrees offreedom for an end effector, the application of shielded and safe (e.g.AEM) electrosurgery energy becomes more complex. The original format ofa rigid shaft instrument that provides shielding and rigidity must bemodified in many ECS applications.

Enhanced control systems including robotic systems, instruments havingwrists, and instruments having flexible shafts impose increased stresson electrosurgical conductors both in monopolar and bipolarimplementations. One example of this type of instrument is the devicedescribed in U.S. Patent Application 2006/0111210A1. This device isrepresentative of the contrast with conventional laparoscopicinstruments having rigid shafts and is representative of the problemssolved by aspects of the present invention. These types of “bendable”and articulating shaft instruments pose an additional problem for theshielding used with traditional AEM technology due to the nature of thebending in the shield area. Conventional AEM instruments utilize a rigidtube conductor as the shield and it is this rigid tube that acts as aconductor for electrical shielding while also providing stiffness to theshaft. In accordance with various aspects of the present invention, theshield used in connection with an ECS system employing AEM monitoringdoes not have to be formed from a rigid material. This shield can bevery flexible as long as it is capable of effectively carrying normaland fault current to the AEM monitor.

In accordance with one aspect, instrument shields may embody one or moreflexible circuit concepts such as a metal coated flexible polymer as theshield conductor. Other embodiments of flexible shields may beconductive rubber, metal braids such as a coaxial cable, metal braidsmolded or extruded inside insulation material, or thin conductive filmsuch as a metalized polymer. Further embodiments such as cloth withwoven conductive fibers, metal or sprayed on conductors may be utilizedas the shield. FIGS. 4A-4D show various embodiments of flexible circuitsthat may be utilized to construct the shield element in monitoring ECSsystems. In addition, one or more of the concepts disclosed in U.S.patent application Ser. No. 11/740,483 may also be utilized to constructthe shield conductors in an ECS system. The details of application Ser.No. 11/740,483 are incorporated by reference in their entirety into thepresent application. As used with the robotic graspers incorporated intomany ECS systems, any of the previously described flexible shieldingtechniques and embodiments can be used to provide a flexible butelectrically safe shield system for AEM technology. In accordance withanother aspect, this technology can also be used for catheters or smallprobes used inter-luminally.

A thin film shield made from cloth, polymer, or other flexible materialsas described above might not prevent an initial arc from generating afault (e.g. broken insulation) condition by penetrating the shield. Inother words, the flexible shield could have a hole burned through itwhen a fault occurs. However, the shield monitor would still sense thefault and begin the sequence of shutting down the energy. In tests thetotal reaction time is less than 10 msec. Therefore, the amount ofenergy dissipated would cause, at most, only superficial damage to theouter insulation of the shield. Accordingly, there is necessarily atrade-off between a thin flexible shield that might allow superficialdamage and a substantially rigid and/or thick flexible shield that wouldprevent the energy from ever reaching beyond the shield in a faultcondition but be more limited in its versatility in complex ECS systems.Further aspects and embodiments of AEM shields used in ECS applicationsare described below. It is contemplated that one or more of theseembodiments made be used either alone or in combination depending on thespecific application and the specific ECS system being developed.

In accordance with one aspect, FIG. 4A shows a shield 400 that comprisesa metalized material 405 disposed over a polymer tubing 410. In anothersimilar aspect, a conductive medium is disposed over a reinforcedplastic or other non-conductive tubing. When utilized with a shieldtube, these types of structures will prevent damage at a fault when thesystem initially breaks down and seeks electrosurgical return throughthe shield system. Systems such as these also have the benefit ofmechanically preventing burns by absorbing fault energy until the AEMmonitor can stop the power output.

In accordance with another aspect, FIG. 4B shows a shield 425 thatcomprises a conductive cloth, wire mesh, or wire braid 430 utilized toform the conductive medium. Other examples include the use of aconductive polymer or elastomer, wire coils such as catheter coiling,embedded wires in a flexible structure or flex circuits such as thoseused in electronics and circuit board structures. While these particularflexible embodiments might not prevent a fault damage because of thepotentially thin layer of material that is used, it can still utilizethe AEM system to stop the power output from the generator. In oneexample test, it was observed that the worst case delay betweeninsulation fault to power cut-off was about 7 msec, including circuitreaction time, and when a relay stopped current flow.

In accordance with another aspect, FIG. 4C shows the cross section of acoaxial cable 440 that includes a center conductor 442 surrounded by asolid layer 444, a foam layer 446 and a shield 448. An outer insulationlayer 449 surrounds the cable 440. The cable 440 uses two types ofprimary insulation, one foamed material 446 with a very low dielectricconstant and one of a conventional material 444. While the foamedmaterial will withstand the voltage in most places, if the foamedmaterial is used alone there will be insulation failures at modestvoltages at particular points (because the randomly arranged bubbles inthe foam line up between the conductors). The conventional materialprotects against failures at those points. Tests have shown goodcapacitance results with low heating, thus in most areas the foamedmaterial is withstanding most of the voltage.

In accordance with another aspect, FIG. 4D shows an embodimentcomprising a layered material based on a fabric matrix. Benefits of thisembodiment include the ability to include such a material as any shapeand the ability to cover the complex geometries found in ECS systems,such as wrists and other mechanical joints. A shield 450 includesinsulating woven matrix 452 with a sprayed on conductor 454 and aninsulating coating 456. Because of the flexibility of the shield 450, itcan be formed into any shape, such as an insulting boot for a wristelement in an ECS system. In another embodiment the shield 450 is formedin place and mimics the outer surface of the instrument it surrounds.

The use of electrosurgical conductors in ECS systems has specific issuesthat need to be addressed in a monitored environment. As mentionedabove, enhanced control systems may employ a wrist or other flexibleelement between the electrode and a support structure (See e.g. FIGS. 1Band 1C) and thus the active conductors and shielding conductors mustalso be flexible in order to follow the same physical path as thesurgical devices and tools. In accordance with another aspect, toaddress this problem, the active and shield conductors may be run in abundled cable assembly such as a coaxial cable where the shieldconductors enclose the active(s) in a portion of the ECS assembly suchas distal flexible elements. This arrangement permits the high-voltageconductors to couple capacitively or by breakdown to metallic componentsof the control assembly and or other end effectors which hold ormanipulate tissue or organs during surgery. In these cases there tendsto be increased capacitive loading, but also reduced opportunity foractive electrical breakdown or capacitive coupling to mechanicalcomponents. Enhanced control systems will have many optical, mechanical,electronic, or hydraulic components contained in compact structures.Thus there is a need for all components, including the electrosurgicalconductors to be compact. FIG. 1C described above shows an example ofthis compact embodiment in a wrist style tool and how all of theintegrated components need to fit within a confined space that moves orotherwise articulates during operation.

A connector for the active electrode can be present at any point in theRF assembly. However any breakdown paths in the connector need to becontrolled so that the most likely breakdown is from active to shieldrather than to an outside conductor. Optimal locations for the connectorare where the environment is dry.

In accordance with another embodiment, a flexible sheath or boot(reusable, limited-use or disposable) may be used to protect againstelectrical conduction from exposed components in the wrist area or otherflexible portion of the ECS system and the patient or users. The sheathor boot may be entirely insulating or shielded with a conductor embeddedin the insulation or on the surface of the insulation. The conductor maybe connected to other conductive components of the ECS system or to aconductor dedicated for the purpose of conducting shielding currents tomonitoring equipment. For example, the fabric matrix of FIG. 4C can beformed to fit over and contour with the surface of an ECS tool as shownin FIG. 1C. In another embodiment, a small caliber flexible AEMconductor may be run through one of the conductor channels 154 or 158 inthe ECS wrist 125 of FIG. 1C.

In general, a shielded electrosurgical conductor may be made morecompact than a non-shielded conductor. This is primarily becausenon-shielded conductors must be made with additional margins of safetyagainst insulation breakdown, resulting in a larger diameter or overallfootprint. In addition, the insulator in a non-shielded conductor mustbe large enough to minimize corona (the local breakdown of air near theoutside of an insulated wire conducting high voltage electrosurgicalenergy). Corona is known to cause heating and produce ozone. Corona canalso cause damage to other components of electrosurgical systems fromassociated chemical mechanisms.

In contrast, a shielded conductor can be constructed with a smallermargin of safety compared to a non-shielded conductor since any failureof the insulation is prevented from causing damage to patients, users,or equipment by the shield and a monitor that causes power shutdownbefore there is any significant damage. Also no corona is produced in ashielded conductor because there is no air subjected to high electricalfield strength. These conditions result in a possible substantialreduction in conductor size. For example, typical non-shielded monopolarelectrosurgical conductors measure 0.090 to 0.120 inches or larger indiameter. A shielded monopolar conductor can be made in the range of0.040 to 0.070″ in diameter. The resulting smaller footprint of shieldedelectrosurgical conductors give them greater utility when incorporatedinto monitored ECS system, particularly those embodiments using bundledcabling or other consolidated conductor arrangements.

As in traditional AEM systems, the shield in ECS and other flexiblesystems is connected to an electrosurgical return or other reference atpatient potential. This is to provide a return path directly to the RFcurrent source for capacitive and fault currents. It also provides theshielding with only a minor effect on RF leakage currents. Conversely,if the shield were returned to earth ground there would be a largeincrease in RF leakage current. This increase is undesirable from thestandpoint of patient safety and also conformance with internationalstandards.

Flexible micro-coax cable can be used in connection with the abovedescribed embodiments. In general, coaxial cable appropriate forelectro-surgery monopolar outputs has high capacitance (20-50 pF/ft).However, the needs in an ECS system for small size, flexibility, andreduced coupling internally may be over a fairly short length, say 2-4feet as opposed to the normal 10′ monopolar conductors. A coaxialstructure with a dual-layer internal insulation system can reduce thecapacitance per unit length and thus increase the length possible for agiven capacitance. In this embodiment, one layer is a conventionalthermoplastic having a relative dielectric constant of 2.0 to 3.5. Thesecond layer is a foamed fluorocarbon having a dielectric constant of1.1-1.3. The net dielectric constant for a system appropriate for highvoltage for example up to 6 KV electrosurgical energy transmission, isin the range of 1.2 to 1.5. This reduces the capacitance per unit lengthof the coaxial structure 30% or more compared to the use of a simpledielectric. Foamed material withstands the voltage in most places.However if the foamed material is used alone there will be insulationfailures at modest voltages, for example 2 KV at particular points. Thisis because the randomly arranged bubbles in the foam line up so thatthere is insufficient insulation thickness in a particular line throughthe material. The conventional material protects against failures atthose points. Tests have shown good capacitance results with lowheating, thus in most areas the foamed material is withstanding most ofthe voltage.

In one example, a coaxial conductor was utilized with the followingcharacteristics:

Component Radius (mil) Description Center 6 25/44 Pri insulation 12.5FEP Shield 7 Spiral 44 ga 99% covered Outer insulation 4 FEP TotalDiameter .059″ +/− .004

As mentioned above, an ECS unit may employ a structure separatelysupported from the patient, surgeons, trocar cannulae, etc. Thesestructures may be supported by a frame attached to the operating room(OR) table or OR floor (See e.g. FIG. 1A). Consequently, electricalbreakdown and leakage may occur between the high voltage conductors andthe ECS frame or other structure. Any such breakdown must result in asafe condition for the patient and users. The support may be comprisedof conductive and insulating components. The ECS structure will likelyhave exposed and/or internal conductive components and insulatingcomponents.

In accordance with another aspect, an ECS system utilizes a speciallydesigned electrosurgical monitoring system. In one embodiment, themonitor has specialized sensing algorithms for each of the differentchannels. Referencing potentials may include the return electrode, areference potential electrode (RPE) earth ground, and a derivedreference and may be different for the separate channels. One suchsystem is described in co-pending U.S. patent application Ser. No.12/257,562 filed on Oct. 24, 2008, the entire details of which areincorporated by reference into the present application. In anotherexample, a dual channel monitoring system as described in U.S. Pat. No.7,422,589 is utilized. The entire details of U.S. Pat. No. 7,422,589 areincorporated by reference into the present application.

In accordance with another aspect, internal ECS metallic components aremonitored for high levels of current and/or power and referenced to theelectrosurgical return. Exposed metallic components are monitored forlow currents and/or powers and referenced to a return electrode (RE),reference potential electrode (RPE), or derived reference (DR). In somecases it may be desirable to utilize an earth ground or an operatingroom table reference. The electrode shield can be monitored for highlevels of current and/or power and referenced to the electrosurgicalreturn electrode (RE). Embodiments described within U.S. patentapplication Ser. Nos. 11/202,605 and 11/202,915 may be relevant inperforming this type of function. The details of these applications areincorporated by reference in their entirety into the presentapplication.

It is desirable to make the shielded flexible sheaths or boots describedabove thin for the purposes of minimizing size and for maintaining theflexibility of the ECS devices. However very thin shields may be limitedin their ability to accept and conduct insulation fault currents. Tocompensate for this, these shields may be adapted to function with afast-responding algorithm to provide for the possibility of temporaryconduction lasting for example 1 msec to a delicate shielding coatingthat partially ablates during an insulation failure. It is anticipatedthat such a shield would have an RE reference, however RPE and DRreferences are also possible.

In accordance with another aspect, ECS monitoring systems may beconstructed as follows in bipolar systems. Two patient-coupledconductors may be contained within a single shield conductor or they mayeach have a separate shield. The monitoring system is preferablycalibrated to indicate that a fault condition may consist of either orboth conductors breaking down to the shielding conductors or to metalliccomponents of the ECS. Given that the shielding conductors are connectedto either RE, RPE, or DR potentials, the breakdown would result in asignificant fraction of the total current being returned through thereferencing connection. Further, in a bipolar application the voltagesfrom each of the active electrodes to the referencing electrode would besignificant. No or low voltage from active to reference would beevidence of a possible insulation failure and that asymmetrical voltagecondition would be a monitored parameter.

In accordance with another aspect, ECS monitoring systems may beconstructed in sesquipolar systems. Sesquipolar systems are monitoredsimilarly to the manner for bipolar systems except that a continuous lowvoltage between the surgically inactive electrode and the referencepotential is considered a normal condition. Thus this condition wouldnot generate a fault response from the monitoring subsystem.

In accordance with another aspect, the electrosurgical generatorsthemselves may be optimized for ECS procedures. For example, thegenerator may have limited power and voltages, for example powers lessthan 80 Watts and open-circuit voltages in the range of 2-4 KV peak(compared to 300 W and 3-5 KV peak for standard monopolar generators).This allows the use of minimally thin insulations and small-gauge cablesin and around highly compact mechanical assemblies such as wrists andelbows. This also results in lower shield currents in normal states ofoperation. In practice, the above limited amounts of power and voltagehave been shown to be adequate for laparoscopic and most forms ofendoscopic surgery not involving fluid environments.

In accordance with another aspect, the electrosurgical generatorincludes output circuitry to compensate for the loading of thecapacitance present in the conductive shield and cabling. Testing hasshown that in standard generators, performance degrades both in opencircuit voltage and loaded power with increasing load capacitance. Forexample, 100 pF results in minimal degradation and 200 pF results in asignificant but tolerable degree of degradation. In some implementationsof ECS systems it may be desirable to support load capacitances in the200-400 pF range. This can be presented by the combination of theelectrode shielding components, the connectors, flexible shieldedconductors and generator leads. Optimized generator output circuitry andinternal feedback control that adjusts the output to account for loadcapacitance are examples of design features that permit calibratedoperation in the presence of high load capacitance.

The electrosurgical generator can also be designed to operate withfrequencies in the low region of the normal operating range offrequencies for general purpose generators of 200-800 KHz, for examplein the range of 200-400 KHz. This will tend to facilitate the use ofhigher load capacitance by reducing the shield currents in the normalstates of operation and allow more effective recognition of abnormalstates of operation.

AEM monitoring components can be implemented in the generator itself inorder to eliminate the need for a separate monitoring hardware. Thiswould tend to reduce cost because of the elimination of the separateenclosure and power supply. It would also increase reliability becauseof the reduced cabling.

In accordance with another aspect, the potentials between theelectrosurgical return electrode and earth ground may be measured and anupper limit placed on these potentials coupled with either an alarm, areduction in applied voltage or the cessation of power in the event of abreach of the limit. The limits are important for patient safety,operator safety, and reduction of interference. Conditions that wouldgenerate high return-ground voltage consist primarily of an abnormallylow impedance between active and ground. ECS systems may present lowactive to ground impedances due to the capacitance inherent in thephysical construction of the system. Thus in these systems it may bedesirable to include an electrical network between return and ground tomaintain an adequately low return to ground voltage. The network mayinclude capacitive, resistive and inductive components.

Normally patient to ground potentials are less than 100 Vrms. However infault conditions such as the active electrode being connected to ground,the potential could rise to a value approaching 10 times that amount.

In accordance with another aspect, an electrosurgical system monitorsfor inadvertent electrosurgical energy in normally non-electrified(“cold”) instruments and other large conductive surfaces. In known AEMimplementations, the primary electrosurgical instrument is continuallymonitored for any stray electrosurgical energy via a multi-wire cord.The multi-wire cord provides both the active conductor for theelectrosurgical and the reference wires for the shield which allows forcontinuous draining of any excessive energy due to capacitive couplingor insulation breakdown.

Current surgical procedures and especially new minimally invasivesurgeries such as SPA procedures described above, place one or moreinstruments and cameras in close proximity to each other to minimize theentry points into the patient's body. Many of these tools andinstruments are “cold” i.e. non-electrified and are generally used toview or handle the tissue in one way or another. Generally speaking, a“cold” instrument is any instrument that is not electrified via a directand intentional electrosurgical connection. The various instruments usedin SPA procedures usually consist of a camera, severalgraspers/dissectors, a “hot” instrument for performing theelectrosurgical procedure, and various other manipulative instruments.It is desirable that the cold instruments also be protected andmonitored to ensure that they remain cold. Most cold instruments are notproperly insulated to deal with an electrical charge and become “hot” orotherwise electrically activated. Activated means that voltage isapplied to the device. In the case of a cold instrument this can occurvia touching the cold instrument with the tip of an activated hotinstrument, through tissue that is contacted by an activated instrumentand the device, via capacitive coupling from a hot instrument, and viainsulation failure from a hot instrument. Even if these cold instrumentsare insulated, the surgical team is not controlling them as if they arehot and may not be utilizing the same precautions as are used when usingan instrument that is intentionally hot. When the electrified instrumentis being used, it can inadvertently transfer RF energy to anotherconductive instrument as described above. The cold instrument may alsobecome energized through loose tissue in the surgical site, for exampleby a cold grasper holding separated tissue while the active electrodeburns it resulting in a non-target tissue being burned by the coldinstrument. A cold instrument may also become hot by the active cablebeing inadvertently attached to the wrong instrument.

Prior systems such as those taught by U.S. Pat. No. 5,312,401 teach thatthe most effective way to prevent stray RF electrosurgical energy fromthe hot instrument is to provide a monitored shielding system thatactively drains any capacitive energy and monitors the draining(reference ground) circuit for excessive energy indicating a faultcondition where the instrument's primary active conductor is shortingdirectly to the shield.

However, in order to protect the cold conductive surfaces frominadvertent or intended RF energy, each of the cold surfaces needs to beboth monitored for excessive voltage and continually drained of any RFenergy, for instance, by providing a referencing connection (ReferencingMethod). A second alternative also exists where the cold conductivesurfaces are monitored for excessive voltage but any excessive energy isnot drained (Monitoring Method). These two aspects are described below.

One method of achieving both referencing and monitoring is to providereference potential for every conductive cold surface via wires that canconduct the energy back to monitoring circuits located in the AEMmonitor. The conductive wires would work similarly to known shieldingcircuits contained within the monitor except each can be in a separatecircuit where individual monitoring parameters can be adjusted toprovide optimum referencing and monitoring. The reference conductors canbe disposable, reposable (partially reusable) or reusable. In oneembodiment, the wires will each electrically connect to the monitoringunit (AEM monitor) at the proximal end and to the conductive coldsurface at the distal end. Connection at the conductive surface can beachieved in several ways depending on the surface. Details of variousconnection methods are described below. As the cold instrument orsurface experiences inadvertent RF electrosurgical energy, the wireacting as a referencing surface will drain away any excessive energy.The monitoring system will also monitor for excessive voltage/currentand control the electrosurgical source according to appropriatemonitoring parameters.

In accordance with another aspect, each of the cold surfaces orinstruments are monitored for excessive voltage. The monitoring of thecold surfaces triggers a monitoring base station (e.g. AEM unit) to shutdown the electrosurgical source and provide an alert to the surgicalteam that a cold surface/instrument has experienced excessive RF energyand that appropriate action needs to be taken such as checking forpatient burns around the instrument in question.

With reference to FIG. 5A, an apparatus 500 for sensing voltage on thesurface of a cold instrument is shown where a generalized instrumentshaft 502 includes a plastic sensing tube or instrumented cannula 504and a pair of dual monitoring contacts 506 and 508. Contacts 506 and 508are connected by leads 510 and 512 to an isolated connection monitor514. In accordance with one aspect, a method of providing electricalsafety to cold instruments used during electrosurgery is as follows. Theinstrumented cannula 504 is used to provide both monitoring andreferencing via dual contacts 506 and 508. Such a tool can be used forthe following scenarios and instruments:

1) An uninsulated conductive instrument whose surface is exposed to thepatient's tissues or users' hands. This type of instrument is neverintended to be activated and become hot.

2) An instrument that is insulated except for a small area at the tip.If activated, this type of instrument is capable of protecting againstconductive discharge through the insulation if the activation voltage iswithin the specification of the insulation.

3) A shielded instrument of the type described in U.S. Pat. No.5,312,401 where the shield is connected to a reference potential througha monitor. The insulated exterior would not be capable of generating asignificant patient or user burn even under the condition of aninsulation fault because of the low voltage between the shield and thetissues.

In any of the above cases, contact sensors 506 and 508 are adapted todetect a voltage (V1) in the instrument 502. Two thresholds are set infirmware located and running within the connection monitor 514. Thesethresholds are compared with the detected voltage V1 and a determinationis made about how to affect the applied voltage to the hotelectrosurgical tool.

A first low threshold is set to result in a safe level of voltage for anuninsulated instrument. In conjunction or in the alternative a secondthreshold is set to a moderate level appropriate to a simply insulatedcold instrument. A shielded instrument would not need to be voltagemonitored, but the same threshold as for a simply insulated instrumentcould be applied.

The dual contacts 506 and 508 are sensed by the connection monitor 514to determine if the instrument surface is conductive. A processingalgorithm uses the conductivity determination to choose between ahigh-level or low-level threshold for an instrument voltage sensor. Forexample, the high level might be 2,000 V peak and the low level 50 Vpeak.

A voltage sensor 516 uses the sensing tube 504 in the cannula whichmeasures the voltage of the instrument outer conductor. It has an outerinsulator and may have an inner insulator. The sensing tube 504 may bedirectly connected to a conductive instrument, or capacitively coupledif there is an inner insulation layer. It will be capacitively coupledto an insulated instrument. The voltage sensor electronics has an inputcapacitive divider that interacts with the intentional and controlledcapacitance of the sensing tube to give an acceptably accuraterepresentation of the voltage on the instrument. The output of a bufferamplifier 518 is detected at 520 (for example peak detected) for aninput to an analog-to-digital converter 522 which than presents the datato a processor 524 implementing an algorithm that uses the data,thresholds, and time to make a determination of acceptable performanceor a fault.

The dual contacts 506 and 508 may also be used to link a conductiveinstrument to a voltage reference. A link (L) may also include anisolation capacitor 517, a current sensor 519, a second detector 521,and second analog-to-digital converter 523 for a monitor. In this casethe low voltage threshold described above is not used and instead acurrent threshold takes part in the fault determination. Thisimplementation will generate fewer false-positive fault determinationsthan a low level voltage sensing due to capacitive coupling among SPAinstruments.

The instrumented cannula system 500 is used to provide referencing andmonitoring for example to a cold instrument having a conductive exteriorsuch as an irrigation tube, and a cold instrument having an insulatedexterior such as a cutting or grasping unit. As mentioned above, in theembodiment of FIG. 5A, two thresholds may be set in the firmware.

In one embodiment a cold instrument may be designed so that it canbecome energized. In this embodiment, cold instruments can be designedwith an adequate outer insulation so that if the metallic tip (a housingor end effector) is touched with the active electrode, the patient wouldnot be injured, assuming that the insulation was intact. In many cases,it is desirable to touch a cold instrument with the active electrode,for example, if the cold instrument is grasping a bleeding blood vessel.Given that the result of detection of a voltage is an alert to the user,it would be beneficial in some cases to inhibit this alert if the actionis intended and safe. Possible design provisions include:

1. Providing a proximity detector in the instrument and cannula assemblyso that the identity of the safe cold instrument is able to inhibit analert.

2. Providing the function of No. 1 above through an optical property ofthe insulator recognized by a detector in the cannula assembly.

3. Providing a shield in the safe, cold instrument that would preventcoupling through the inner wall. The shield would be connected to thereturn.

In the diagram of FIG. 5A, the reference ground is provided to provide astable (quiet from an RF standpoint) reference for the sensing amplifierA₁. Several options are available for the configuration of FIG. 5A.

In one embodiment, the reference ground should generally be an easilyobtainable connection point, be electrically quiet (low RF noise oroffset) and have some level of independence from the generator/monitor.

In another embodiment, the shield may be a direct connection to theshield in an AEM system. While this connection is easily obtainable in ahardware based system, there might be several tens of volts of RF noisedue to the voltage drop of return current flowing through the returnelectrode connection impedance and also the shield current flowingthrough the shield coupling capacitor.

In one embodiment, the return electrode is a direct connection to thereturn electrode in an AEM system. The same noise problems exist as withthe shield described above. The return electrode would then requirereliable isolation because this is a patient connection.

In another embodiment, the reference potential electrode is as describedin U.S. Pat. No. 7,465,302. This embodiment solves the problem of noisefrom return electrode voltage drop. However it would require a separatepatient electrode which may or may not be housed in the same assembly asthe return electrode. While this might introduce connection impedance,it should be of negligible consequence for this connection alone.

In another embodiment, the derived reference can be embodied asdescribed in U.S. Pat. No. 7,465,302. This is a subsystem whose purposeis to avoid the need for a separate RPE and to provide an effective lowimpedance connection, while also providing an accurate representation ofthe voltage of the target tissue. It is estimated that this wouldpresent noise of only a few volts.

In another embodiment, the circuit ground is provided by the ground ofthe low voltage signal processing inside the AEM monitor. In anyhardware based system this is easily obtainable. Its use would mean thatno decoupling circuitry would be required for the detected signals.However, the noise could be expected to be significant.

In yet another embodiment, the environment reference is provided bycoupling via an antenna to the general operating room ground. This isuseful because it would not involve the design of the cannula or need awired connection. However, the connection impedance would be extremelyhigh and it could be expected to have noise equal to that of the circuitground option. Additionally, there could be expected to be a large RFvoltage component coupled from the instrument being measured which wouldreduce the effective differential signal level and also reduce accuracy.

In another embodiment, the abdominal wall reference is the potential ofthe abdominal wall in contact with the surgical cannula. A metalinterior tube would be included in the cannula wall. This would beseparate from the inner wall of FIG. 5A above and would be positioned tocouple directly to the abdominal wall. It could conductively contact thetissue or capacitively couple to the tissue through a thin plasticinsulation. This would provide a very quiet signal since there would beno significant electrosurgical current flowing through this region ofthe tissue.

FIG. 5B shows a more specific embodiment of a multi-channel monitoringsystem used in a known ECS system. With reference to FIG. 5B, a complexrobotic ECS system 530 typically includes two or more robotic armassemblies 532, 534, 536, and 538, but more or less may be provided.Each robotic arm assembly is normally operatively connected to one ofthe master controls of a control station 115 or other surgeon consolesuch as described in FIG. 1A. Thus, movement of the manipulator portionof the robotic arm assemblies is controlled by manipulation of themaster controls at the control station 115.

Each of the robotic arm assemblies 532, 534, 536, and 538 comprises alinkage that supports and includes a removable surgical instrument ortool 540, 542, 544, and 546, respectively. The tools 540, 542, 544, and546 of the robotic arm assemblies may include various types of endeffectors and may also include an image capture device, an endoscope ora similar tool. Exemplary embodiments of such a surgical system can befound in U.S. Patent Application No. 2009/0192524, the details of whichare incorporated herein by reference in their entirety.

Another embodiment of achieving referencing in a system such as thatdescribed in FIG. 5B is to provide conductive channels for everypotentially dangerous conductive cold surface in order to conduct theenergy away from the surface. In accordance with this aspect, amulti-channel monitor 550 is connected to a plurality of monitoringchannels 552, 554, 556, and 558. Each of the channels 552, 554, 556 and558 consists of a conductor (e.g. a wire), a monitoring channel, and areference potential. A potentially dangerous conductive cold surface isany surface that can come in contact with a patient or user that is notintended to conduct energy such as the tools 540, 542, 544, and 546 ofthe robotic arm assemblies described above. The reference conductors canbe disposable, reposable (partially reusable) or reusable. In oneembodiment, the wires will each electrically connect to the monitor atthe proximal end and to the conductive cold surface of the tools 540,542, 544, and 546 of the robotic arm assemblies at the distal end.Connection at the conductive surface can be achieved in several waysdepending on the surface. As the cold instrument or surface experiencesinadvertent RF electrosurgical energy, the wire connecting thereferencing surface will drain away any excessive energy. As shown inFIG. 5B, the types of surfaces that may be referenced include the bodyof a driving mechanism, a non-insulated instrument shaft, an instrumenttip, and/or a support structure. Any of these surfaces may come incontact with a patient or a user and cause injury if significant energyis transmitted at the point of contact. Different reference potentialsmay be assigned for each conductive surface being monitored.

It is desirable to implement monitoring in each referencing channel sothat dangerous conditions will cause an alert and excessive energy willbe prevented. The monitoring system 550 monitors for excessive voltage,current, power or energy as, for example, disclosed in U.S. patentapplication Ser. No. 12/257,562 and controls the electrosurgical sourceaccording to appropriate monitoring parameters which may be differentfor each type of surface. The monitoring of the cold surfaces triggersthe monitoring system to reduce power or shut down the electrosurgicalsource. An alert is provided to the surgical team that a coldsurface/instrument has experienced excessive RF energy and thatappropriate action needs to be taken such as resolving an instrumentcollision and checking for patient burns around the surface in question.

In accordance with another embodiment, the monitoring circuit comprisesa base unit (such as a modified AEM monitor) and individual sensor tags.Each of the tags attaches directly to the conductive surface to bemonitored. The tags can be wired, or wireless and provide communicationback to a central location where the base unit is connected to theelectrosurgical power source and capable of shutting down ESU powershould excessive voltage be detected at a tag. In various embodimentsthe tags include RF tags such as found on most merchandise or clothing,most of which tend to be passive. In addition, active tags can also beutilized (active meaning they have their own power source) usually foundin tracking/inventory applications. The tags can be disposable,reposable (have both a disposable and reusable element), or reusable.The tags can also have visible/audible indicators. The indicators canprovide one state such as a green light for working, and a second statefor alert mode such as a flashing red light indicating the tag hassensed excessive RF energy. The indicators will help the operating roomstaff quickly identify which of the multiple tags has de-activated theESU and therefore needs to be accessed for damage to the patient.

For both the referencing and the monitoring methods described above, thewired or wireless tags can attach to the multiple “cold” surfaces invarious ways. For the cases where the metal of the surface to monitor isdirectly exposed, the wired or wireless tag needs to be simply attached,electrically conductive, to the metal surface. This can be achievedthrough adhesive, mechanical attachment or other methods that place aconductive surface of the wire and/or tag directly to the metal coldsurface. In this case, the monitoring assembly can be fully disposable,or have a disposable element such as the adhesive tag and a reusableelement such as the wire. For the case where the cold surface to bemonitored cannot be directly accessed by the tag or wire, a capacitiveassembly is integrated with the surface to be monitored. For example,many of the current electrosurgical instruments are insulated to preventaccidental exposure of active components if the instrument is used“hot.” Therefore, direct access to the metal of the instrument is notpossible without damaging the instrument. By placing a conductive tubearound this instrument and electrically monitoring any current flowthrough this tube, or voltage if a known reference is used, RF energycan be detected. The “tube” thus forms a capacitor with the instrument.The tube can take many shapes and forms so long as a capacitor withsufficient surface area is formed. Examples are described below.

FIG. 6 shows one embodiment of a surgical instrument 600 that generallyincludes a handle portion 602, a shaft 604 and an end effector 606. Inorder to monitor the voltage present in the instrument shaft 604, aclamp sensor 610 including an RF tag 614 is placed at some point alongthe length of the shaft 604. The clamp sensor 610 forms a capacitivetube that can monitor voltage in the instrument shaft 604. The voltageis in one embodiment referenced against the surrounding air for any highoccurrences of voltage that might indicate a dangerous situation for thepatient. If high voltage is detected, the sensor 610 communicates withthe AEM monitor which then inactivates the electrosurgical generator. Asdescribed above, the tag can be wireless or wired directly to the AEMmonitor and can also include an LED indicator to show which of thewireless tags sensed the over-voltage.

FIGS. 7A and 7B show another embodiment of a sensor used to monitor anycold instruments or other surfaces. In FIG. 7A a surgical instrument 700generally includes a handle portion 702, a shaft 704 and an end effector706. In order to monitor the voltage present in the instrument shaft704, an adhesive sensor 710 that includes sensor layers 712 and an RFtag 714 is placed at some point along the length of the shaft 704. Thesensor 710 forms a capacitive structure that can monitor voltage in theinstrument shaft 704. If high voltage is detected, the sensor 710communicates with the AEM monitor through the tag 714 which theninactivates the electrosurgical generator. FIG. 7B shows a detail of thesensor 712 including an insulation layer 720, a conductive layer 722, asecond insulation layer 724 and an adhesive layer 726. While the sensor710 is shown attached to a surgical instrument, the nature of thisembodiment lends itself well to attaching to other flat surfaces such asan operating room table, the robotic arm of an ECS surgical system oreven a person performing some aspect of the surgery.

FIG. 8 shows a view of a single point entry procedure performed througha single incision 800 that utilizes one hot electrosurgical instrument802 and two cold instruments 804 and 806. In one embodiment one of thecold instruments is a camera, although the same principles apply to anycold instrument used in such a procedure. In FIG. 8, cold instrumentsensors 808 and 810 are attached to cold instruments 806 and 804 andmonitor those instruments for any undesired voltage and relay thisinformation back to the monitor for action that may need to be takensuch as shutting down power to the electrosurgical instrument 802. Inthe embodiment of FIG. 8, the sensors can utilize either of the clamp oradhesive style sensors described above.

In another embodiment, the sensors can be rechargeable and available foruse from a docking or other storage and/or charging station. At thediscretion of the operating room staff, one or more sensors can beapplied to any surface that may need monitoring for voltage orelectrosurgical energy. Depending on the procedure, more or less of thesensors may be necessary or otherwise called for. Either of the clamp oradhesive style of the sensors described above are easily applied toinstruments and/or other surfaces at a moments notice and at thediscretion of the operating room staff.

FIG. 9 shows a wired version of the sensors where three instruments 902,904 and 906 are each accessing a surgical site through a single incision900. Sensors 908, 910 and 912 are coupled to the three instruments, andare wired back to an AEM monitor 920 through conductors 914, 916 and918. In this embodiment, the sensors are incorporated into the cannulasof the instruments 902, 904 and 906 and are generally not removable orinterchangeable by a user. Instead, an OR staff person would connecteach of the sensors to the AEM monitor 920 with the conductors 914, 916and 918. This wired embodiment provides for a continuous drainage ofcurrent for any of the instruments.

FIG. 10 shows a generalized ECS system setup 950 that utilizes cold toolmonitoring as described above. The system 950 includes an ECS system 952coupled or otherwise in communication with an operating room table 954upon which a patient 956 is positioned. The OR table 954 may includeother structures and/or surfaces such as a table mount 958. OR staff orsurgeon 960 is present at some point during a surgical procedure.Sensors 962, 964, 966, and 968 are placed at various points in thesystem. In the example of FIG. 10, a sensor is placed on the ECS system,any tools or other actuation devices coming from the ECS system, theoperating table, the table mount and the OR staff person. As can beappreciated, any surface that is desired to be monitored can have asensor included and that is tied back to a monitoring device such as anAEM monitor.

The above connection methods provide several alternatives that canminimize cost, ease of attachment, variations of surfaces to monitor,and preference of the surgical team although alternative connectionmethods may also be used such as clip-on brackets, elastic or rigidstraps, magnetic strips, or fasteners.

Turning now to FIGS. 11-15, various embodiments of end effectors withflexible shields related to the previously-illustrated instrument aredescribed in further detail.

FIG. 11 illustrates a side section view of the distal region of asurgical instrument 1100. The instrument 1100 has an electrode 1102 andan end effector 1104 for carrying out a surgical procedure on a patient.The end effector 1104 is articulably coupled to the distal end 1124 ofan instrument segment 1126, and the end effector 1104 may comprise orcarry the active electrode 1102 to perform an electrosurgical procedure.

A flexible housing 1106 is provided to carry the end effector 1104 andelectrode 1102, and the flexible housing 1106 may be, in someembodiments, a tubular flexible tube, and as just one example, a plasticor polymer resin comprising perfluoroalkoxy alkane (PFA). Portions ofthe flexible housing 1106 may be surrounded or substantially surroundedby a flexible shield 1108 according to some embodiments. The flexibleshield 1108 may comprise a conductive material, such as a conductivewire mesh as will be described in further detail in subsequent sectionsof this disclosure.

Continuing with FIG. 11, an outer insulator 1110 may be disposed aboutthe flexible shield 1108 to provide a barrier between the instrument1100 and the patient. The outer insulator 1110 may comprise, forexample, a plastic such as ethylene tetrafluoroethylen (eTFE). Putsuccinctly, the flexible housing 1106 carries the end effector 1104, aswell as a steering mechanism 1112, which may be a steering wire, formanipulating the electrode 1102, and, taken together, the flexiblehousing 1106, flexible shield 1108, and outer insulator 1110 provide apath for electrical current to flow in a prescribed manner.

The flexible shield 1108 is configured to transmit both a normal current1114 and a fault current 1118 to an active electrode monitoring system(not illustrated in FIG. 11) during an electrosurgical procedure. Theflexible shield 1108 may also be shaped and positioned to maintain anadequate creepage spacing between the flexible shield 1108 and theelectrode 1102, which may sometimes be referred to as an activeelectrode, such as for effectuating a surgical procedure.

Before describing an adequate creepage spacing in further detail, thoseskilled in the art will understand that, as illustrated in FIG. 11, aphenomenon known as creepage breakdown can occur, in which stray current1120 between a shield such as the flexible shield 1108 and the surgicalregion 1122 of the electrode 1102 may occur, if the shield or flexibleshield 1108 is positioned too close to the electrode 1102, for example,by allowing current to pass through the patient. The embodimentillustrated in FIG. 11 is configured with an adequate creepage spacingso as to prevent stray current 1120 from occurring.

Adequate spacing along the end effector surface of 3 to 5 mm perkilovolt is one feature that reduces or eliminates the chance ofcreepage breakdown. Specifically, in some embodiments, a space of atleast 3 millimeters per kilovolt is maintained between the distalmostportions of the flexible shield 1108 and the most proximal portions ofthe surgical region 1122 of the electrode 1102.

However, even in cases in which adequate spacing has been provided, thesurface of the end effector 1104 may become contaminated with blood,which is an electrical conductor, thus increasing the chance ofbreakdown. Therefore, to overcome this problem, in some embodiments, theouter insulator 1110 may be configured to enclose, surround, or overlapon onto the end effector 1104. Put another way, the outer insulator 1110may extend further distally than does the flexible shield 1108.

In some embodiments, a sealing feature 1128 between the outer insulation1110 and the end effector 1104 may be provided. The sealing feature 1128may be achieved using, for example, an interference fit between theouter insulator 1110 and the end effector 1104. In some embodiments, thesealing feature 1128 may be achieved by chemically etching the innersurface 1130 of the outer insulator 1110 and applying a cyanoacrylateadhesive on the outer surface 1132 of the end effector 1104 (orotherwise between the outer insulator 1110 and the end effector 1104.

Turning now to FIG. 12, it illustrates a shield section 1200 of asurgical instrument, having a primary polymer insulator 1202, aconductive coating 1204, and an outer insulator 1206. In someembodiments, the conductive coating 1204 is applied to the primarypolymer insulator 1202, which may be a flexible insulating tube, by wayof a physical vapor deposition method, a carbon-filled silicone, or aconductive fabric sleeve. In some embodiments, instead of a conductivecoating 1204, the shield section 1200 may include a layer that iscomprised of a number of conductive segments coupled together by way ofa mechanical interlock, thereby providing a desired amount offlexibility and/or rigidity in a variety of given directions.

With reference now to FIG. 13, a cross section illustrates a coaxialcable 1300 that includes a center conductor 1342 surrounded by a primaryinsulator 1344, a shield 1346, and an outer insulator 1348 suitable foruse in some embodiments, such as for coupling the shield to a monitor.

The center conductor 1342 may comprise a copper wire having a size of 32AWG at a minimum, such that the outer diameter of the copper wire is nomore than about 0.008 inches. Sizing the center conductor 1342 in thismanner allows for a loading of about 1.0 A current and 300 Watts ofpower, at a 25% maximum duty cycle and 300 Ohms, which is a typical loadresistance of monopolar electrosurgery. The center conductor 1342 mayalso accommodate higher bursts of current for very short periods oftime, for example up to about 2.5 Amperes, due to load resistanceexcursions to as low as 100 Ohms, for example, 50 milliseconds. Thoseskilled in the art will understand that the duration of the high burstsof current may be minimized due to a rapid temperature rise after theelectrode 1104 is brought into contact with fresh tissue. Specifically,after an initiation of current, the heating of the tissue forms a steambarrier between the electrode 1104 and tissue being cut or coagulated.Sparks through the steam may dissipate power and create additionalimpedance, thereby reducing the flow of current to 1.0 Amperes or below.

Continuing with FIG. 13, the primary insulation 1344 may be a PFA aspreviously described herein, due to having a 2000 Volts per millimeterdielectric strength and 2.03 dielectric constant. Selection of PFA insome embodiments may allow the primary insulation to have a 0.006 inchthickness or less, while also being capable of withstanding up to a 5.0kilovolt maximum peak electrosurgical voltage—with a margin of over100%. The low dielectric constant of the primary insulation 1344 alsoresults in minimum capacitance for any given geometry. The primaryinsulation 1344 may therefore, in some embodiments, be selected to havea dielectric strength of 2,000 Volts per mil (0.001 inches) or greater,and a dielectric constant of 2.03 or greater.

The flexible shield 1346 illustrated in FIG. 13 may comprise amulti-strand braid of 44 AWG copper wire. This provides a sufficientconductive pathway for fault currents to flow for brief durations, forexample less than 100 milliseconds if a breach is formed in the primaryinsulation 1344. Due to braiding, the thickness of the flexible shield1346 may be twice the diameter of the individual strands, or about 0.004inches.

Continuing with FIG. 13, the outer insulation 1348 may comprise an eTFE(ethylene tetrafluoroethylene) layer as previously described herein, andmay be 0.0025 inches this, or less. An eTFE may be selected due to therelative resistance against abrasions (comparted to PFA), although eTFEhas a lower dielectric strength of 1,000 Volts per millimeter, ascompared to PFA. This dielectric strength is adequate because in shieldmonitoring systems, the impedance between shield and electrosurgicalreturn is low compared to the active impedances, for example 30 Ohms.Thus, even if fault currents are over 2.0 Amperes, the transient shieldvoltage is limited to under 100 Volts. In some embodiments, aninstrument having an outer insulation 1348 with a dielectric strength of1,000 Volts per millimeter may be selected or provided.

The net outer diameter OD of the coaxial cable 1300 may be 0.035 inchesor less in some embodiments. In some embodiments, a coaxial cable 1300having an outer diameter OD of 0.025 inches or less may be provided byreducing the thickness of the primary insulation 1342 to, for example,0.0045 inches. In some embodiments, a coaxial cable 1300 having an outerdiameter OD of 0.015 inches or less may be provided by further reducingthe thickness of the primary insulation 1342. These embodiments providea margin of less than 100% but may still be adequate in someembodiments.

In some embodiments, the flexible shield 1346 may be, instead of amulti-strand wire braid, a coating, such as those created by physicalvapor deposition (PVD) methods. In some embodiments, the flexible shield1346 is a coating of 1.0 mil (0.001 inches) or less. In someembodiments, the coating is deposited on the primary insulator 1344 byPVD methods. Those skilled in the art will understand that, as thecoating becomes thicker, flexibility may be reduced; therefore, a thincoating, if used, may be selected to maintain flexibility of theflexible shield 1346.

In some embodiments, the flexible shield 1346 may be formed by aspirally wound copper wire, which allows the net thickness of theflexible shield 1346 to be equal to the strand diameter of the spirallywound copper wire. An advantage of the spirally wound copper wire as theflexible shield 1346 is that it introduces little to almost noresistance to flexing, in addition to a relatively thin cross section.

In some embodiments, the flexible shield 1346 comprises a polyaniline ora carbon-filled silicone or epoxy, although, due to the lowerconductivity (compared to copper) of these materials, the overallthickness of the coaxial cable 1300 would necessarily increase.

In some embodiments, the flexible shield 1346 may comprise an extremelythin layer of graphene, which is a material known to have very highconductivity. In some embodiments, the flexible shield 1346 may comprisea graphene layer having a thickness of 0.004 inches or less. In someembodiments, the flexible shield 1346 may comprise a graphene layerhaving a thickness of 0.002 inches or less. In some embodiments, theflexible shield 1346 may comprise a graphene layer having a thickness of0.001 inches or less. In some embodiments, the flexible shield 1346 maycomprise a graphene layer having a thickness of 0.0005 inches or less.

In some embodiments, the flexible shield 1346 may comprise a corrugatedshield structure.

Turning now to FIG. 14, a flexible shielded wall structure 1400according to some embodiments is now described in further detail. Theflexible shielded wall structure 1400 may have a primary insulator 1402,a shield coating 1404, and an outer insulator 1406. Those skilled in theart will understand that the flexibility of a flexible shielded wallstructure 1400, using a conductive shield coating 1404 as the shieldelement may tend to introduce rigidity; however, providing etchedregion(s) 1408, such as a spiral etch of the coating 1404 in areasintended to flex provide the ability to flex without fracture. Anynumber of etching methods and patterns can be envisioned, and should notbe limited to the embodiment illustrated in FIG. 14.

Turning now to FIG. 15, in some embodiments, an insulating shielded boot1500 may be provided to shield an electrosurgical instrument, such asthat illustrated in FIG. 1C. The boot 1500 may have a first layer 1502having a flexible non-conductive material, a second layer 1504 disposedon or about the first layer 1502 and having a flexible conductivemedium; and a third layer 1506 disposed on or about the second layer1504 and having a flexible non-conductive material. The boot 1500 isconfigured to isolate an electrosurgical active conductor 150 and towithstand a power having a voltage of up to 5 kilovolts or a faultcurrent of 2.0 Amperes or greater. The boot 1500 has a proximal end anda distal end, with the distal end having an elastic material 1510 tomaintain the boot 1500 in position relative to the electrosurgicalinstrument and/or to prevent debris from entering a gap between the boot1500 and the electrosurgical instrument.

The boot 1500 is coupled to at least one shield conductor 1512 orredundant shield conductors 1512, 1514. The shield conductors 1512, 1514are configured to transmit normal current and fault current to an activeelectrode monitoring system, such as that described in described in U.S.Pat. No. 5,312,401 and related patents, during an electrosurgicalprocedure. The boot 1500, in a manner similar to that described withreference to the flexible shield 1346 previously described herein, maysurround at least a portion of an instrument segment, and the boot 1500may be shaped and positioned to maintain an adequate creepage spacingbetween the boot 1500 and the active electrode 150.

With reference now to FIG. 16, a surgical tool assembly 1600 may havehave a boot 1601 substantially similar to the boot 1500 described withreference to FIG. 15, and an electrosurgical instrument with anarticulable end effector 135. The boot 1601 may surround a portion ofthe end effector 135, an elongated segment 130 of the surgical too, andan articulation mechanism 125, so as to shield those portions of theelectrosurgical instrument that may come into contact with patienttissue, except the end effector 135. The boot 1601 may maintain anadequate creepage spacing as previously described herein, and may havefirst, second, and third layers 1602, 1604, 1606 and shield conductors1612, 1614 as previously described with reference to FIG. 15.

The boot 1500, 1601 may have a metal coated flexible polymer and anouter insulator, coupled to one or more shield conductors 1512, 1514,1612, 1614.

In some embodiments, the booth 1500, 1601 has a conductive rubber, acoaxial cable, a metal braid inside an insulation material, or a thinconductive film.

The boot 1500, 1601 may have a conductive coating disposed over aflexible polymer tubing.

The boot 1500, 1601 may have a shielded cable having a maximumcross-sectional dimension of 0.035 inches or less, and the boot 1500,1601 may be configured to conduct up to 300 Watts of power having avoltage of up to 5 kilovolts.

In some embodiments, the boot 1500, 1601 comprises polyaniline,carbon-filled silicone, graphene, conductive epoxy, or a physical vapordeposition on an insulating material.

In some embodiments, the booth 1500, 1601 comprises at least one of aconductive fabric, braided wire, a wire mesh, a spiral wire, or aconductive coating on a flexible insulating material.

In some embodiments, the boot 1500, 1601 comprises a plurality ofconductive segments joined by mechanical interlocks in a mannersubstantially as previously described with reference to FIG. 12.

Those skilled in the art can readily recognize that numerous variationsand substitutions may be made in the invention, its use and itsconfiguration to achieve substantially the same results as achieved bythe embodiments described herein. Accordingly, there is no intention tolimit the invention to the disclosed exemplary forms. Many variations,modifications and alternative constructions fall within the scope andspirit of the disclosed invention as expressed in the claims.

What is claimed is:
 1. An active electrode probe for an enhanced controlsurgery system, comprising: a flexible conductor for deliveringelectrosurgical energy during an electrosurgical procedure, theconductor being adapted for connection to an electrosurgical generator;a flexible electrical insulation substantially surrounding theconductor; a flexible conductive shield substantially enclosing theelectrical insulation, the flexible conductive shield electricallyconnected to a reference potential, whereby any current which flows inthe flexible conductive shield from the conductor is conducted to thereference potential.
 2. The probe of claim 1, wherein: the flexibleconductive shield comprises a conductive cloth.
 3. The probe of claim 1,wherein: the flexible conductive shield comprises a wire mesh.
 4. Theprobe of claim 1, wherein: the flexible conductive shield comprises awire braid.
 5. The probe of claim 1, wherein: the flexible conductiveshield comprises at least one of a wire coil, a catheter coil, anembedded wire in a flexible structure, or a flex circuit.
 6. The probeof claim 1, wherein: the flexible conductor is a monopolar conductor;and the flexible shield is substantially cylindrical with an outerdiameter of between 0.040 inches and 0.070 inches.
 7. The probe of claim6, further comprising: an active electrode monitoring system configuredto stop power from flowing through the probe within 7 milliseconds of aninsulation fault.
 8. The probe of claim 1, further comprising: a coaxialcable having the flexible conductor, a solid layer surrounding theflexible conductor, a foam layer surrounding the solid layer, and ashield surrounding the foam layer; and an outer insulation layersurrounding the coaxial cable.
 9. The probe of claim 1, furthercomprising: a shield having a woven matrix with a sprayed on conductorand an insulating coating.
 10. The probe of claim 1, wherein: theflexible substrate is a foam material.
 11. An electrosurgicalinstrument, comprising: an instrument segment having a proximal end anda distal end; an end effector articulably coupled to the distal end ofthe instrument segment, the end effector having an active electrode andconfigured to perform an electrosurgical procedure; and a flexibleshield configured to transmit normal current and fault current to anactive electrode monitoring system during the electrosurgical procedure,the flexible shield surrounding at least a portion of the instrumentsegment and a portion of the end effector, the flexible shield shapedand positioned to maintain an adequate creepage spacing between theflexible shield and the active electrode.
 12. The electrosurgicalinstrument of claim 11, wherein: the flexible shield comprises a metalcoated flexible polymer.
 13. The electrosurgical instrument of claim 11,wherein: the flexible shield comprises a conductive rubber, a coaxialcable, a metal braid inside an insulation material, or a thin conductivefilm.
 14. The electrosurgical instrument of claim 11, wherein: theflexible shield comprises a conductive coating disposed over a polymertubing.
 15. The electrosurgical instrument of claim 11, wherein: theflexible shield comprises a shielded cable having a maximumcross-sectional dimension of 0.035 inches or less; and the flexibleshield is configured to conduct up to 300 Watts of power having avoltage of up to 5 kilovolts.
 16. The electrosurgical instrument ofclaim 11, wherein: the flexible shield is corrugated.
 17. Theelectrosurgical instrument of claim 11, wherein: the flexible shieldcomprises polyaniline, carbon-filled silicone, graphene, conductiveepoxy, or a physical vapor deposition on an insulating material.
 18. Theelectrosurgical instrument of claim 11, wherein: the flexible shieldcomprises at least one of a conductive fabric, braided wire, a wiremesh, a spiral wire, or a conductive coating on a flexible insulatingmaterial.
 19. The electrosurgical instrument of claim 11, wherein: theflexible shield comprises a plurality of conductive segments joined by amechanical interlock.
 20. The electrosurgical instrument of claim 11,wherein the flexible shield comprises: a first layer having a flexiblenon-conductive material; a second layer disposed on the first layer andhaving a flexible conductive medium; and a third layer disposed on thesecond layer and having a flexible non-conductive material overlapping aportion of the end effector; wherein the flexible shield is configuredto isolate the active electrode; withstand electrical excitation havingan open-circuit voltage up to 5 kilovolts peak, normal current up to 1.5amperes, and fault current up to 2.5 amperes; and inhibit creepageelectrical breakdown.
 21. The electrosurgical instrument of claim 11,wherein the flexible shield is a boot positioned about an articulatingportion of the electrosurgical instrument and exposing a portion of theend effector.